/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.expression.spel.ast;

import java.lang.reflect.Array;

import org.springframework.asm.MethodVisitor;
import org.springframework.asm.Type;
import org.springframework.expression.EvaluationException;
import org.springframework.expression.TypedValue;
import org.springframework.expression.spel.CodeFlow;
import org.springframework.expression.spel.ExpressionState;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

/**
 * Represents a reference to a type, for example
 * {@code "T(String)" or "T(com.somewhere.Foo)"}.
 *
 * @author Andy Clement
 */
public class TypeReference extends SpelNodeImpl {

    private final int dimensions;

    @Nullable
    private transient Class<?> type;


    public TypeReference(int pos, SpelNodeImpl qualifiedId) {
        this(pos, qualifiedId, 0);
    }

    public TypeReference(int pos, SpelNodeImpl qualifiedId, int dims) {
        super(pos, qualifiedId);
        this.dimensions = dims;
    }


    @Override
    public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
        // TODO possible optimization here if we cache the discovered type reference, but can we do that?
        String typeName = (String) this.children[0].getValueInternal(state).getValue();
        Assert.state(typeName != null, "No type name");
        if (!typeName.contains(".") && Character.isLowerCase(typeName.charAt(0))) {
            TypeCode tc = TypeCode.valueOf(typeName.toUpperCase());
            if (tc != TypeCode.OBJECT) {
                // It is a primitive type
                Class<?> clazz = makeArrayIfNecessary(tc.getType());
                this.exitTypeDescriptor = "Ljava/lang/Class";
                this.type = clazz;
                return new TypedValue(clazz);
            }
        }
        Class<?> clazz = state.findType(typeName);
        clazz = makeArrayIfNecessary(clazz);
        this.exitTypeDescriptor = "Ljava/lang/Class";
        this.type = clazz;
        return new TypedValue(clazz);
    }

    private Class<?> makeArrayIfNecessary(Class<?> clazz) {
        if (this.dimensions != 0) {
            for (int i = 0; i < this.dimensions; i++) {
                Object array = Array.newInstance(clazz, 0);
                clazz = array.getClass();
            }
        }
        return clazz;
    }

    @Override
    public String toStringAST() {
        StringBuilder sb = new StringBuilder("T(");
        sb.append(getChild(0).toStringAST());
        for (int d = 0; d < this.dimensions; d++) {
            sb.append("[]");
        }
        sb.append(")");
        return sb.toString();
    }

    @Override
    public boolean isCompilable() {
        return (this.exitTypeDescriptor != null);
    }

    @Override
    public void generateCode(MethodVisitor mv, CodeFlow cf) {
        // TODO Future optimization - if followed by a static method call, skip generating code here
        Assert.state(this.type != null, "No type available");
        if (this.type.isPrimitive()) {
            if (this.type == Boolean.TYPE) {
                mv.visitFieldInsn(GETSTATIC, "java/lang/Boolean", "TYPE", "Ljava/lang/Class;");
            } else if (this.type == Byte.TYPE) {
                mv.visitFieldInsn(GETSTATIC, "java/lang/Byte", "TYPE", "Ljava/lang/Class;");
            } else if (this.type == Character.TYPE) {
                mv.visitFieldInsn(GETSTATIC, "java/lang/Character", "TYPE", "Ljava/lang/Class;");
            } else if (this.type == Double.TYPE) {
                mv.visitFieldInsn(GETSTATIC, "java/lang/Double", "TYPE", "Ljava/lang/Class;");
            } else if (this.type == Float.TYPE) {
                mv.visitFieldInsn(GETSTATIC, "java/lang/Float", "TYPE", "Ljava/lang/Class;");
            } else if (this.type == Integer.TYPE) {
                mv.visitFieldInsn(GETSTATIC, "java/lang/Integer", "TYPE", "Ljava/lang/Class;");
            } else if (this.type == Long.TYPE) {
                mv.visitFieldInsn(GETSTATIC, "java/lang/Long", "TYPE", "Ljava/lang/Class;");
            } else if (this.type == Short.TYPE) {
                mv.visitFieldInsn(GETSTATIC, "java/lang/Short", "TYPE", "Ljava/lang/Class;");
            }
        } else {
            mv.visitLdcInsn(Type.getType(this.type));
        }
        cf.pushDescriptor(this.exitTypeDescriptor);
    }

}
